Method of liberation of pure nitrogen and oxygen from air

ABSTRACT

A METHOD OF LIBERATION OF PURE NITROGEN AND OXYGEN FROM AIR BY WAY OF LIQUEFACTION OF SAID AIR ON THE CYCLE OF AVERAGE OR HIGH PRESSURE AND SUBSEQUENT FRACTIONATION, ACCORDING TO WHICH METHOD AIR IS DIVIDED PRIOR TO FRACTIONATION INTO TWO FLOWS, OF WHICH ONE COOLED BY HEAT EXCHANGE WITH THE NITROGEN FRACTIONATION PRODUCT, WHILE THE OTHER FLOW IS COOLED BY COMPRESSED OXYGEN AND AN ARGON FRACTION WHICH ARE LIKEWISE FRACTIONATION PRODUCTS.   D R A W I N G

Basin et al.

METHOD OF LIBERATION OF PURE NITROGEN AND OXYGEN FROM AIR Inventors: Genrikh Maxovich Basin, ulitsa Gorkogo, 8, kv. 8; Ilya Vladimirovich Gorenshtein, ulitsa Lenina, 48, kv. 14; Mark Eleazarovich Lemberg, prospekt Shevchenko, 8a, kv. 19; Semen Grigorievich Linetsky, Krasnoflostky pereulok, 9/6; Anatoly Eliseevich Myasoed, ulitsa Gagarina, 8, kv. 23; Yakov Benediktovich Zanis, ulitsa Tolstogo, l3, kv. 3 all of Odessa, U.S.S. R. 3

Filed: Nov. 3, 1971 Appl. N0.: 195,421

Related US. Application Data l1 Sept. 25, 1973 [58] Field ofSearch ..62/22,27,28,29,38,41

1 1 7 References Cited UNITED STATES PATENTS 102,801 9/1963 Fetterman ..62/4l 3,086,371 4/1963 Schilling .;..62/41 2,779,174 1/1957 Vesque .;....62/29 3,110,155 11/1963 Schuftan ..62/38 Primary Examiner- Norman Yudkoff Assistant Examiner- Arthur F. Purcell Attorney Eric H. Waters, Harold L. Roditi, John G.

' Schwartz and .1. Harold Nissen 1 ABSTRACT A method of liberation of pure nitrogen and oxygen from air by way of liquefaction of said air on the cycle of average or high pressure and subsequent fractionation, din tq l iqhm hgsiair iasl vis ednr ar to fractionation into two flows, of which one is cooled by heat exchange with the nitrogen fractionation prod- Continuation of Ser. No. 770,027, October 23. 1968, now abandoned.

uct, while the other flow is cooled by compressed oxygen and an argon fraction which are likewise fractionation products.

U.S.Cl ..62/29,62/13,62/22,62/41 SCl m J aWPI Flgure Int. Cl ..F25J 3104, F25J 3102' 5*" LIZ] l l5 1 I H 5 1 f2 N E METHOD OF LIBERATION OF PURE NHTROGEN AND OXYGEN FROM AIR This application is a continuation of copending application serial No. 770,027 filed Oct. 23, 1968, and 5 the heat exchange between the obtained nitrogen and now abandoned.

The present invention relates to methods of liberation of pure nitrogen and oxygen from air.

in the prior art method of liberation from air of pure MN/sq.m and cleaned of moisture, carbon dioxide and other high-boiling admixtures. The unit MN/sq.m is mega Newtons per square meter, which is the equivalent of about Kg. sq. cm. according to the international Cl system.

The cleaned air is divided into two parts, of which one is cooled by nitrogen and compressed oxygen, and the other by an argon fraction, in two respective .heat exchangers. Through the first heat exchanger there passes air, which is then directed for expansion into an expander and to a throttle valve.

Air directed to the expander is removed from said first heat exchanger at a temperature of 50 to 100 C, while air directed to the throttle valve is at a temperature of 160 to 165 C.

The second part of air is cooled in the second heat exchanger to a temperature of 130l35 C. After cooling the air in the heat exchangers, the second part the initial air in the three-flow heat exchanger by way of utilizing effective heat-exchange surfaces, such as those formed by finned pipes or finned plates, due to high consumption of labor when manufacturing heat I nitrogen and oxygen, the air is compressed t 3 5 .0 10 exchangers with said elements.

Since the three-flow heat exchanger passes the greater part of air cooled to low temperatures (of the order of l60 to l65 C), the coaxial pipes should be of relatively great length and, consequently, the heat exchanger is of relatively great weight.

It is an object of the present invention to eliminate the above-mentioned disadvantages.

In accordance with this and other objects, the present invention seeks to develop an economically feasible method of separation of air that facilitates a chn .sqnrsr eusmr y sm fi ts t heatexchange surfaces, such as those formed by finned pipes or finned plates.

Accordingtp the invention, one part of compressed air is cooled by nitrogen, and the other part by compressed oxygen and the argon fraction.

It is expedient to divide the compressed air so that the part of said air cooled by nitrogen to 1.5-3 times of the air is mixed with a portion of the first part of greater than the part of the air cooled by the comthe air directed for throttling, expanded in the throttle valve and directed into a fractionating column.

The part of air expanded in the expander is likewise directed into the fractionating column.

pressed oxygen and the argon fraction.

The method of liberation of pure nitrogen and oxygen from air, according to the present invention. makes it possible to cool the greater part of the air Nitrogen leaving the fractionating column is diin a double-flow, i.e., two streams heat exchanger rected under a pressure of 0.05 MN/sqm into the first heat exchanger as a coolant.

Liquid oxygen is removed from the fractionating column with the aid of a pump, compressed to 20 with the employment of effective heat-exchange surfaces.

The second heat exchanger, in which the second part of the air is cooled by the argon fraction and the MN/sq. and forced into the Same heat exchanger, compressed oxygen, is a three-stream exchange likewise as a coolant.

in said heat exchanger, liquid oxygen is gasified and heated to a temperature from 8 to 30C, owing to the heat exchange with the air. Nitrogen and oxygen with bare coaxial pipes.

Compressed oxygen is passed inside the pipes of small diameter, initial air is passed in the circular gap between the coaxial pipes, and the argon fraction leaving said heat exchanger are directed to the is passed inside the shell in the interpipe space.

consumer.

in order to simultaneously obtain pure nitrogen and oxygen, the argon fraction is removed from the fractionating column and directed under a pressure of 0.05-0.06 MN/sq.m into the second heat exchanger as a coolant. Said argon fraction is thereafter discharged into the atmosphere or used for recovering the adsorbent of the cleaning unit, in which initial compressed air is cleaned of mositure and other highboiling admixtures. The first heat exchanger is a threeflow one and, as a rule, comprises coils of coaxial pipes, compressed oxygen being passed in the inside one of the latter pipes, while cooled air is displaced Since the load in said second heat exchanger is but a small part of the total heat load, the weight of said heat exchanger is relatively small.

Besides, said heat exchanger lets through the smaller part of air cooled to a relatively higher temperature (from 135 to 145 C) and, therefore.

' it becomes possible for the coaxial pipes mounted in the heat exchanger to be considerably shorter and relatively few in number.

The present invention is further exemplified by a description of the preferred manner for carrying out the present method of liberation of pure nitrogen and oxygen from air, with referenace to the accompanying in the circular gap between the coaxial pipes, inside drawing, the sole figure of which diagrammatically The known method is disadvantageous in that the efficiency of the heat exchange between nitrogen and air in a three-flow heat exchanger is relatively low,

shows of the invention the process.

Connections are designated in the drawing as follows:

air; 0 oxygen; N nitrogen; Fr argon fraction.

Prior to entering the heat exchangers, the air is divided into two parts.

The larger part of the air (60 to 75 percent of the total amount) is delivered via pipelines 4 into the heat exchanger 2, passed inside the finned pipes (shown diagrammatically in the drawing) and cooled by a counterflow of nitrogen to 145155 C. From the zone of the heat exchanger 2, in which the air temperature reaches 701 10 C, a part of the air (45 to 62 percent of the total amount) is removed and directed via pipeline 5 into an expander 6, wherein the air is expanded, performing useful work, to the pressure in the fractionating column 8.

Then, via pipeline 7, the air is delivered for fractionation into the fractionating column 8.

The remaining, smaller, part of the air (25 to 40 percent of the total amount) is delivered via pipeline 9 into the other, three-flow, heat exchanger 3.

In the heat exchanger 3, the air is passed in a circular gap between coaxial pipes are diagrammatically (said pipes shown in the drawing) and cooled to a temperature of l35145 C by two counterflows, viz., compressed oxygen passing inside the pipes of smaller diameter and of the argon fraction passing inside the heat-exchanger shell.

The part of the air cooled in the heat exchanger 2 is discharged via pipeline 10, while that cooled in the heat exchanger 3 is discharged via pipeline 11. Then, said parts of the air are mixed, expanded in a throttle valve 12 and directed into the fractionating column 8.

Nitrogen, obtained as a result of liberation from the a r, s l vcre via p in 1.3;, d r agrsss of up to 0.05 MN/sq.m, into the inter-pipe space of the heat exchanger 2, where it exchanges heat with air passing inside the latter heat exchanger, is heated to a temperature 2 to 5 C lower than that at the inlet to the heat exchanger 2 and further directed to the consumer.

Liquid oxygen, obtained as a result of liberation from the air, is removed from the fractionating column 8 and, via pipeline 14, delivered to a liquid oxygen pump 15, by which the oxygen is forced under a pressure of up to 20 MN/sq.m via pipeline 16 into the three-flow heat exchanger 3, in which the oxygen is heated with the purpose of gasification, whereupon said oxygen at a temperature 2 to 3 C lower than that of the compressed air (at the inlet to the heat exchanger 3) is directed to the consumer.

The amount of nitrogen obtained is 65 to 72 percent, while that of oxygen is to 19 percent, of the total amount of air.

In order to simultaneously obtain pure nitrogen and oxygen, the argon fraction in an amount of 10 to 22 percent of the total amount of air is removed from the fractionation column 8 and delivered under a pressure of up to 0.05-0.6 MN/sq.m via pipeline 17 into the shell of the three-flow heat exchanger 3, in which said I oxygen from air, differing from the above-described one, for example by the absence of the expander.

The installation designed for carrying out the method according to the present invention, with the hourly output of 600 cu.m of nitrogen and 85 cu.m of q mpr sqs o y en; i about 0 .k. i b r than the known installations of the same capacity.

We claim:

1. A method of liberating pure nitrogen and oxygen from air, comprising the steps of compressing the air, purifying the air of high-boiling impurities, dividing the purified compressed air into a first larger stream and a second small stream, the ratio of the first air stream to the second air stream being in the range between 1.5-3:l.0, cooling the first stream of said air in a heat-exchanger consisting of two streams wherein the air undergoes heat exchange solely with the obtained gaseous nitrogen, cooling the second stream of said air in a heat-exchanger consisting of three streams wherein the air undergoes heat exchange with compressed liquid oxygen and with a gaseous argon fraction obtained from the air to leave the three-stream heat exchanger at a temperature between 1;l 5 to 1515? C, thg sec o nd stream of air passing in entirety and without diversion through the three-stream heat exchanger, removing a portion of the first stream of cooled air consisting of 45-62 percent of the total air supplied from an intermediate point in the two stream heat exchanger at a temperature of to ll0 C, expanding the thus removed portion of the first stream by causing it to perform useful work, mixing the remaining portion of the first stream after discharge thereof from the two stream heat exchanger at a temperature of to .5."." s\xith he, entire rscco drs a of the cooled air, throttling the latter mixture, mixing the expanded portion of the first air stream and the thus throttled mixture, subjecting the thus mixed expanded streams to low-temperature fractionation to liberate gaseous pure nitrogen, and pure liquid oxygen together with gaseous argon fraction in an amount of 10 to 22 percent of the starting amount of air, compressing the liquid oxygen fraction in a liquid-oxygen pump, and subsequently utilizing said liberated products for cooling the divided streams of compressed and purified air in the heat exchangers.

2. A method according to claim 1 wherein the air and nitrogen flow in counterflow in the two-stream heat exchanger.

3. A method according to claim 1 wherein the air flows in counterflow with the oxygen and argon fraction in the three-stream heat exchanger. 

